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  1. #1
    toglho Guest

    Default Hafco AL-250G thread cutting limitations

    I'm currently looking to replace my third lathe (AL-50G) that I've just sold. I've narrowed it down to the Workman 10x20 (same as Grizzly), the Paramount 610x280, impala 550x250 and Hafco's AL250G. All have 25mm or better spindles, 250 swing or better and 500 centres or better. The paramount has a reverse gear as an added extra as does the Impala, (I think); however, parts for the first three may prove problematic. Hafco have excellent spares availability, even for some of their now defunct machines. The Hafco rep advised me the AL-250G would cut imperial threads, I was (nearly) satisfied with that, until I took a look at the threading chart on the headstock and pulled out my calculator. He was partially correct: For example the finest thread it will cut is (metric pitch) .035, in imperial threads that's 725 TPI. Perhaps there is an imperial thread that fine, but I think you'd need a microscope to see it and so it goes for the next 15 or so pitches. The finest thread I would use ( metric pitch .70) is around 36 TPI. The remaining nine or so metric pitches are useable, but when converted to imperial TPI, the conversion matchups are exceedingly rare. Unless my maths aren't up to speed (and feel free to correct me) the AL250G is basically useless for cutting imperial threads. Hafco have nothing between the AL50G and the AL320 that's suitable for me, so, I'll have to again look at the other brands that I've already mentioned. All three look alright on paper, except for requiring the use of the half nuts for auto feed and suspect spare parts availability (half nuts). Although much cheaper than Hafco, and, with a long list of standard accessories, such as a stand, 4 jaw chuck, live centre, etc, the (un) availability of spares could turn all three into expensive boat anchors. Now the question is: Can I get by with just metric thread cutting? Oh whoa is me, what a quandry. Will someone please prove my maths wrong on the AL-250G's thread cutting limitations.

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  3. #2
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    Spares are not usually a problem because you can generally make your own (or get some help from someone else if it's something broken that stops the lathe from working. These lathes are not rocket science.
    I looked up the AL250G at Hare and Forbes. They quote the metric threads as being 0.25mm to 2.5mm pitch (10 pitches available) L149 | AL-250G Bench Lathe | machineryhouse.com.au
    It looks as if all the standard pitches are there so you should not have problems with metric threads. It does not look like it comes with a way to do imperial (it's not as simple as selecting the closest one). That would worry me but it depends on what you want to do. You may need to get a conversion gear made up and do some maths to work out your imperial threads if you want them. Ask the the sales guy how you do imperial threads on it, and nominate a specific thread eg 18 tpi just to make sure you don't get a vague answer.

    Michael

  4. #3
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    Hi toglho,
    Welcome,
    You're confusing powerfeed and screwcutting I think.

    http://images.machineryhouse.com.au/L149/3/700
    The 15 on the left are feeds(engaged with the little handle on the carriage the red arrow points at http://images.machineryhouse.com.au/L149/10/700), the 15 on the right are pitchs (engaged with the half nuts, the large lever in the last link).

    As for cutting imp thread you would need a compound gear. (I think 63/60 is used on some smaller lathes, 120/127 on others)

    Stuart

  5. #4
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    toglho,

    Ditto as Michael stated.........I think you may be reading too much into the chart....your lathe has a metric lead screw and whatever combination of Imperial thread you are after, you will need to set the gear chain to the equivalent of the 127 ratio to get a direct correlation to Imperial.......I have the AL320 with it's metric lead screw and with the gears supplied, have no dramas cutting Imperial - should clarify that...the lathe has no issues....

    There are heaps of programs out there that allow you just to input the gears available and the pitch wanted to give you the nearest value which your chart may not show : and if you find an error factor that won't let you get a 100% match then you can always make or get the correct gear for it..........I've never needed to even though some may not be that 100% match......for example with the gears supplied, I cannot cut 27tpi exactly, but they do allow a combination for 26.94tpi..........you'll find that's pretty much the case right through unless you achieve the 127 ratio in the gear chain....wish my work had such a small error factor.......please correct me if I've misread your point here......???..........Lee

  6. #5
    Ueee's Avatar
    Ueee is offline Blacksmith, Cabinetmaker, Machinist, Messmaker
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    Hi toglho,
    The 250 has a metric leadscrew, and I have to say that owning a machine with a metric screw is a PITA as it seems to limit the range of threads availiable unless you have a huge range of change gears. As some on this forum know I am pretty disappointed with my hafco mill, and would suggest buying a good second hand machine over a new Chinese one.
    Ewan

  7. #6
    toglho Guest

    Default Al250

    Geez, this is a busy site, four replies in one night. I just wanted someone to check my math, long time since I've had to convert metric pitch to TPI (25.4/pitch - correct). Nevertheless, I think your probably right: The feed/pitch chart on the left side of the chart, while clearly marked as pitch, more than likely refers to feed speeds, 725 TPI certainly seems excessive, but by the same token, 15 feed speeds!!! One chart fits all, me suspects. The problem with the AL-250 is the largest thread is listed as 2.5. Where do you stop spending time, effort and money on the thing to get it to do what you want, a 127 tooth gear for imperial screw cutting, another set of gears to reverse gear it and still more to increase the pitch variations.. I had to do that with my other lathes: Reverse tumblers, 4 bolt compound, the list goes on and on. General Tools in Adelaide, the Hafco distributors, don't have the AL250, the rep wasn't even aware of it, he certainly wasn't very helpfull and he wanted to charge another $150 for a 4 jaw chuck and another $150 on top again just to get one in, I don't think it even comes with a chip tray. So without seeing the machine, it's very difficult to judge what mods are necessary, how easy/difficult or time consuming the job of modifying will be and how much the end product is going to cost me. I had my heart set on the AL-54B and wasn't aware it had been discontinued until after I sold my AL-50, comes down to doing your homework I guess. I'll either have to decide if I can get by with just metric threads, or look at one of the others I mentioned, their certainly better value for the money and parts for the workman should be available from Grizzly in the US.

  8. #7
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    Be aware that Grizzly have a $200 minimum international order.

  9. #8
    toglho Guest

    Default Grizzly

    Thanks for that Bryan, who would have thought!!! Helps in choosing the right lathe.

  10. #9
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    Could it be an engineering thing? Maybe the lathe isn't built to handle larger pitches??

    I'm just thinking aloud but the pitch chart on my lathe states the available pitches as 0.2 - 3.0mm and 8 - 24tpi. Both of these end with a major diameter close to 25mm. There are fine pitches that give you larger diameter but course pitch is standard.

    In actual fact I can get pitches as high as 8mm and as low as 4tpi. That's up around 100mm major diameter. Maybe the manufacturer didn't intend for me to cut large diameter threads.

    On a side note a lot of the larger threads use very similar gearing and in some cases half of them are just there to fill the space so they needed ones can mesh.

  11. #10
    Dave J Guest

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    I see your replacing you 3rd lathe, I would say in a few years time you will find the limitations of this lathe and be replacing your 4th lathe with a 300 x 900 one.

    A few guys have asked about this size lathe and while some guys have them and seem to do fine, I would recommend if you can afford it to jump strait to a 300 x 900mm lathe and be done with buying any more lathes. It will be something you will have for many many years to come and may never get rid of it ever. I have one and I do some pretty big stuff sometimes and it takes all I can throw at it, and then on the other hand it will do intricate parts.

    It's up to you, but like I said if you can spare the bit extra it will save you down the track. You can usually find them around second hand as well, so you might get one for the same price as this lathe.

    Dave

  12. #11
    toglho Guest

    Default Al 300

    The Al-300 was my second lathe, but I found it just too big, so went down to the AL-50. The AL-300 was an excellent lathe, good thread selection, power crossfeed, large spindle bore, etc, but I found it just too big. This time I'm going to a 250mm swing with 25mm spindle bore, should be just right. Incidently, my first lathe was made in Taiwan, same as the AL-50G but without the gearbox. Unfortunately, the bed wore severely in only a couple of years, have had no such problem with the Chinese models. Going out on Wednesday for another look at the Paramount, Impala and Workman, but, the Hafco AL-250G is looking like the best bet at the moment, with a geared head, back gear, 80rpm low gear, 26mm bore and power crossfeed, but mostly, because of good spares availability: Very hard to make your own parts with a broke lathe, as I found out with the AL300 (an embarassing mistake that we won't go into).

  13. #12
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    Quote Originally Posted by slhouetteV8 View Post
    Could it be an engineering thing? Maybe the lathe isn't built to handle larger pitches??

    I'm just thinking aloud but the pitch chart on my lathe states the available pitches as 0.2 - 3.0mm and 8 - 24tpi. Both of these end with a major diameter close to 25mm. There are fine pitches that give you larger diameter but course pitch is standard.

    In actual fact I can get pitches as high as 8mm and as low as 4tpi. That's up around 100mm major diameter. Maybe the manufacturer didn't intend for me to cut large diameter threads.

    On a side note a lot of the larger threads use very similar gearing and in some cases half of them are just there to fill the space so they needed ones can mesh.
    Not to sure what you were trying to convey in your reply regards Pitch/TPI in relation to thread OD.

    As long as the depth of thread is less than the OD of the material diameter doesnt matter when cutting threads.

  14. #13
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    [QUOTE=slhouetteV8;1457242]
    I'm just thinking aloud but the pitch chart on my lathe states the available pitches as 0.2 - 3.0mm and 8 - 24tpi. Both of these end with a major diameter close to 25mm. There are fine pitches that give you larger diameter but course pitch is standard.

    In actual fact I can get pitches as high as 8mm and as low as 4tpi. That's up around 100mm major diameter. Maybe the manufacturer didn't intend for me to cut large diameter threads.

    QUOTE]

    HI Sil
    In reality you can cut any pitch or TPI on any diameter. Say for whitworth, 1" diameter is 8 TPI, you can cut 1, 2, 3, 4, 5 etc etc TPI on that diameter. You could even invent your own range of threads so long as you screwcut nuts to suit. As pipeclay says "As long as the depth of thread is less than the OD of the material diameter doesnt matter when cutting threads." Well two depths of thread anyway.

    Phil

  15. #14
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    I think there is a limit set by the lowest rpm the lathe will do and the pitch of the lead screw. On my lathe (75rpm and 8tpi leadscrew) to turn 4tpi the leadsrcew is turning at 150rpm. 2tpi 300rpm, 1tpi 600rpm. On a 1200mm long unsupported shaft.....

    Of course if you really want those sort of pitches you can(I'm told) drive the lathe with the leadsrew...... but thats different.

    Stuart

  16. #15
    Dave J Guest

    Default

    Quote Originally Posted by toglho View Post
    The Al-300 was my second lathe, but I found it just too big, so went down to the AL-50. The AL-300 was an excellent lathe, good thread selection, power crossfeed, large spindle bore, etc, but I found it just too big. This time I'm going to a 250mm swing with 25mm spindle bore, should be just right. Incidently, my first lathe was made in Taiwan, same as the AL-50G but without the gearbox. Unfortunately, the bed wore severely in only a couple of years, have had no such problem with the Chinese models. Going out on Wednesday for another look at the Paramount, Impala and Workman, but, the Hafco AL-250G is looking like the best bet at the moment, with a geared head, back gear, 80rpm low gear, 26mm bore and power crossfeed, but mostly, because of good spares availability: Very hard to make your own parts with a broke lathe, as I found out with the AL300 (an embarassing mistake that we won't go into).
    It sounds like you exactly what your after in the size of the lathe. Just remember a VFD can be fitted to get the speed down and a lot of guys here have them fitted.

    It's funny you say that about Taiwanese lathes, I know of a few Taiwanese lathes where the owners are not happy with them, but as far as my Chinese lathe I couldn't be happier.
    Dave

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